Spouses of chronic pain patients may play important roles in reinforcing pain behaviors and disability, according to hypotheses derived from operant reinforcement theory. However, no studies have directly tested this proposition. This project will investigate, using direct observational assessment, interactions between chronic pain patients and their spouses to examine (a) the extent to which pain behaviors are followed by differentially reinforcing spouse responses; (b) the relationship of patterns of patient-spouse interaction to marital discord, depression, and disability; and (c) the relationship of pretreatment interactional patterns to outcome following multidisciplinary inpatient treatment. Eighty chronic back pain patients and their spouses will participate. Assessment will be conducted at hospital admission, discharge, and six months and one year posttreatment. At admission, patients and spouses will complete measures of the patient's functional disability, pain behavior and spouse's response, as well as of psychological functioning and marital satisfaction. They will also be videotaped while engaging in a series of interactional tasks, which will be scored using a system for coding sequential patterns of patient and spouse behaviors. The study will provide a direct test of fundamental assumptions of the operant model of chronic pain behavior, and may have direct implications for treatment. Spouse involvement in treatment, a costly aspect of many pain programs, may be critical to success in some cases but unnecessary in others. The delineation of family interaction patterns and mediating variables which may be related to treatment outcome is an essential first step in identifying the most appropriate treatments for individual patients.